The calculator uses the Haversine formula to figure out the great-circle distance between two points from their lat/long in decimal degrees. It treats the Earth as a sphere (mean radius 6,371 km) so you get a proper aerial distance instead of the flat-map approximation. That’s what you want for microwave path surveys, line-of-sight checks, and antenna alignment, especially when a few extra meters can mess with your fade margin and link budget.

Azimuth (the initial or forward bearing) is simply the compass direction you’d face at Site A to point straight at Site B, measured clockwise from true north. It’s calculated with the usual spherical trig using the arctangent of the sine and cosine of the longitude difference and the two latitudes. Because the Earth is a sphere, the back azimuth from B to A isn’t always exactly 180° opposite, particularly on longer paths. So the tool works out the return bearing separately to keep things accurate for long-haul links.

You can enter coordinates either as decimal degrees or in degrees-minutes-seconds (still common in older site surveys and regulatory filings). There’s also a simple compass rose that shows the direction of Site B relative to Site A at a glance—handy when you’re out in the field trying to get the antenna mount roughly pointed before you start fine-tuning with a spectrum analyzer or alignment scope.